1. Field of the Invention
The present invention relates to systems and methods for drilling in the earth. More specifically, the present invention relates to enhanced reaming assemblies and methods for use in horizontal directional drilling.
2. Description of Related Art
In many circumstances, it is desirable to form a hole along a controllable path. For example, when utility lines are to be laid underneath a road, building, or other structure, it may be desirable to drill a generally horizontal hole in the ground rather than forming a trench in which to lay the utility lines. This type of drilling is commonly referred to as “horizontal directional drilling,” or “HDD.”
According to some known horizontal directional drilling methods, a pilot hole of comparatively small diameter is first formed. The pilot hole is made through the use of a steerable drill bit that is tracked and controlled from the surface. After the pilot hole has been formed along the desired pathway, the pilot hole may be broadened, or “reamed,” and the utility lines may be drawn through the hole. A “reamer” is driven and rotated through the pilot hole to perform the reaming operation. A “back reamer” is a reamer that is drawn through the pilot hole, for example, through the use of a drill pipe that also conveys drilling fluid to the back reamer. A reamer may also be pushed through the pilot hole in a manner similar to that of the steerable bit used to form the pilot hole.
Known reamers have a number of limitations. For example, many known reamers wear out rapidly and therefore have a short operating life. Many such reamers have a unitary structure. Thus, excessive wear of any part of the reamer necessitates replacement of the entire reamer.
Some reamers are only usable with a narrow range of subterranean formation types. Thus, multiple reamers may need to be taken to a given job site. If a formation change is encountered during drilling, the entire reamer may need to be replaced with a reamer more suitable for penetrating the new formation.
Furthermore, many known reamers penetrate too slowly. Slow penetration increases the cost of the reaming operation because the motor and pump must sustain more wear and the drilling crew must spend more time at the site to complete the hole. Yet further, many known reamers become clogged or fouled by cuttings from the reaming operation, and must therefore be withdrawn from the hole and re-inserted to continue reaming.
Accordingly, a need exists for a reaming system and method capable of rapidly reaming a pilot hole. Additionally, a need exists for a reamer with exceptional wear resistance, in which parts can be field-replaced to enable continued use of less worn portions of the reamer. Furthermore, a need exists for a reamer that can be easily adapted for different subterranean formation types. Yet further, a need exists for a reamer that facilitates passage of cuttings out of the hole to enable uninterrupted reaming.